1. FIELD OF THE INVENTION
This invention relates to an air cooling apparatus utilized for cooling air in a space, such as an air cooler in a refrigerating showcase of a freezing and refrigerating system, a cooler for a refrigerating warehouse, an evaporator of an air conditioner, an outdoor heat exchanger of a heat pump of the air cooled type or a brine heat exchanger.
2. DESCRIPTION OF THE PRIOR ART
FIG. 1 is a schematic sectional view in explanation of a typical example of air cooler of the prior art. The air cooler comprises a plurality of fins 2 arranged in substantially parallel relationship with a predetermined spacing therebetween and located between side plates 1, and heat transfer tubes 3 extending through the fins 2 in a plurality of positions in the fins 2.
The air flowing through the fins 2 of the air cooler is cooled, through the fins 2 and heat transfer tubes 3, by a refrigerant flowing through the heat transfer tubes 3.
In this type of air cooler, the moisture in the air condenses and changes into frost which forms on the surfaces of the air cooler. The frost formation tends to markedly reduce the cooling capacity of the air cooler.
If the amount of frost formed on the surfaces of the air cooler increases, the frost will interfere with the flow of the air through the air cooler. Therefore, in order to maintain the cooling capacity of the air cooler at a desired level, it is necessary to effect defrosting of the surfaces of the air cooler from time to time. In one type of processes known in the art for removing frost, the frost is melted by heating. This type of processes include a process in which the air is heated by a heater mounted at the upstream end of the path of the air current with respect to the fins so as to feed the heated air to the air cooler to effect defrosting thereof. Another process relies on spraying of the air cooler with water, warm water or brine. In still another process, a thermal refrigerant is circulated through the portions of the air cooler where the frost formation has taken place. These processes are described, for example, in GUIDE AND DATA BOOK (SYSTEMS), 1970, by ASHRAE, at pages 339-340.
When the frost is heated by heating for the purpose of effecting defrosting, the air cooler must be temporarily shut down while a defrosting operation is being performed. In case the air cooler is utilized for freeze storing of perishable goods, such as foods, a rise in the temperature of the foods will cause deterioration thereof. In case the air cooler is used with an air conditioner, it is impossible to perform air conditioning while defrosting is being performed. Moreover, additional energy will be required for heating the frost, and piping and valves must be provided to carry out warm water spraying or refrigerant circulation. Such being the case, air cooling apparatus of the prior art utilizing conventional defrosting processes have the disadvantage of the increased cost of production of the air cooling apparatus.